Current medical treatment frequently involves the extracorporeal treatment of blood, that is, blood is removed from a patient's body, treated, and then returned to the patient. Thus, for example, during the course of open heart surgery, blood is removed from a patient, oxygenated in a suitable oxygenating device, and returned to the patient. In the case of kidney malfunction or failure, blood is removed and treated, for example, in a dialyzer to remove toxic metabolites. The purified blood is then returned to the patient.
In the above or other instances, it may be necessary or desirable to add certain additives to the blood. For example, where blood is being dialyzed or oxygenated, heparin or a similar anticoagulant may be added to the blood after it has been withdrawn from the patient and before it is dialyzed or oxygenated.
In still other instances, it may be desirable to add reactants to the blood after it has been taken from a patient in order to achieve a desired medical effect. For example, it has been proposed to treat sickle cell anemia by a process which includes reacting a patient's blood with cyanate ion in a suitable extracorporeal device. See Vol. XX, Transactions of the American Society of Artificial Internal Organs, page 574 (1974).
In extracorporeal treatments, such as those mentioned above, the temperature of the blood taken from the patients corresponds to the patient's body temperature which, in normal circumstances, is about 98.6.degree. F. The extracorporeal environment to which the removed blood is exposed has a temperature which is considerably lower, usually about 68.degree. F. to 72.degree. F. Heat exchangers may be employed in such instances in order to insure that blood returned to the patient has the desired temperature. Heat exchangers are also employed in extracorporeal blood circuits where it is desired to either raise or lower the temperature of the blood after it has been withdrawn from the patient and prior to its treatment or reaction thereof.